[3.0] Theme split (wave 9, part 2) — clear the post sections with inline-end

[albertlast]

Description

Part 2 of wave 9 of the #7933 split.

index.css clears .signature, .attachments, .under_message and the two custom field
blocks in one rule, and rtl.css mirrored three of the five. clear: inline-end
follows the writing direction, so the override is no longer needed and all five behave the
same as each other.

Why wave 8 skipped this, and why it is safe now

Wave 8 (#9571) converted every clear whose override was an exact mirror, and deliberately
left this group alone: the two that rtl.css does not mirror would change the side they
clear in a right-to-left language, which is a behaviour change rather than a no-op.

That turns out not to matter, because the clear does nothing to any of the five.

The same rule also gives them width: 100% and overflow: auto. overflow: auto makes
the box a block formatting context root, and such a box does not overlap a preceding float
— at full width it cannot sit beside one either, so it is already pushed below it. That is
exactly what the clear was asking for. The declaration has been redundant all along,
which is why nobody noticed the two missing mirrors.

Measured, not assumed

Toggling clear through none, left, right and both on all five elements — in both
writing directions, at 1280px, 700px and 470px wide:

none of them moves by a single pixel.

Only .under_message renders on the test forum's posts (no signature, attachments or
custom fields on them), so the other four were injected into the live document in their
real position in order to be measured.

Then the usual sweep of 18 pages, recording clear, float, display and the bounding
rectangle of every element, before and after, captured back to back:

	elements	differences
left-to-right	4732	1 — the clear keyword itself
right-to-left	4732	1 — the same keyword

No geometry changed in either direction. The right-to-left result is the one that matters,
since that is where two of the five swap the side they clear.

rtl.css goes from 366 lines to 361. With this, every clear in the theme that can be
expressed logically is.

Issues References (Fixes|Related|Closes)

Part of the #7933 split; finishes the clear work started in #9571.

🤖 Generated with Claude Code